The invention relates generally to earth retaining walls. More particularly, the invention relates to a modular retaining wall system composed of a plurality of wall blocks that are provided with locking means for precluding forward leaning or tipping of the blocks. Further, the invention pertains to retaining means for attaching reinforcement members to the retaining wall in between mating courses of wall blocks formed in the retaining wall.
Modular earth retaining walls are commonly used for architectural and site development applications. Such walls are subjected to very high pressures exerted by lateral movements of the soil, temperature and shrinkage effects, and seismic loads. Therefore, the backfill soil typically must be braced with tensile reinforcement members. Usually, elongated structures, commonly referred to as geogrids or reinforcement fabrics, are used to provide this reinforcement. Geogrids are often configured in a lattice arrangement and are constructed of a metal or polymer while, reinforcement fabrics are constructed of a woven or nonwoven polymer fiber. These reinforcement members typically extend rearwardly from the wall and into the soil to stabilize the soil against movement and thereby create a more stable soil mass which results in a more structurally secure retaining wall.
Although several different forms of reinforcement members have been developed, difficulties remain with respect to attachment of the members to retaining walls. In particular, the reinforcement members can shift out of position and be pulled out from the retaining wall due to movement of the soil. This difficulty can be especially problematic in areas of high seismic activity. In response to this problem, several current retaining wall systems have been developed to retain geogrid reinforcement members. Rake shaped connector bars are transversely positioned in the center of the contact area between adjacent stacked blocks with the prongs of the connector bar extending through elongated apertures provided in the geogrid to retain it in place. Despite adequately holding the geogrid in position under normal conditions, this system of attachment provides a substantial drawback. Specifically, the geogrids of the system only extend along the back halves of the contact areas between the blocks. Although the geogrids are relatively thin, this partial insertion of the geogrids can cause the retaining wall to bow outwardly due to the aggregate thickness of the geogrids. As can be appreciated, this outward bowing can be substantial with tall retaining walls that require a multiplicity of geogrids. Aside from creating the impression of instability, this condition increases the likelihood of wall failure, particularly in response to seismic activity.
Another problem associated with the construction of modular retaining walls is securement of the blocks to each other within the wall. Various connection methods are currently used in retaining wall construction to interlock the blocks. In one known system, blocks having bores inwardly extending within their top and bottom surfaces are provided for the receipt of dowels or pins. In addition to limiting shifting of the blocks, these pins are used to retain geogrids. Where a geogrid is to be inserted between two courses of stacked blocks, the pins are inserted into the bores with the pins extending through the apertures of the geogrid. Although providing some resistance against block shifting, the actual strength of the block-to-block connection is generated by the friction between the block surfaces. Therefore, shifting can occur. Moreover, the pins do not lock the upper blocks to the lower blocks. Accordingly, severe seismic activity can cause the upper blocks to jump from their foundations and topple downward. Additionally, when the pins are made of metal, they will corrode over time due to the infiltration of moisture from the surrounding environment.
In another known retaining wall, an upper surface of the blocks includes a projection and a lower surface of the blocks includes a cavity into which the projection can extend. Although the provision of these projections and cavities avoids the corrosion problem associated with the pins of the previously described system, similar to that system, no positive locking mechanism is provided to retain the upper blocks on top of the lower blocks. Therefore, this system is susceptible to toppling in response to strong seismic activity. In addition, construction of the walls is complicated by the fact that the top course of blocks must be held in place when the backfill soil is poured to prevent the blocks from being pushed over the edge of the wall.
It can therefore be appreciated that there exists a need for a mechanically stabilized wall system having secure retaining means for maintaining reinforcement members in their proper positions within the wall. Accordingly, it is to the provision of such an improved mechanically stabilized retaining wall system that the present invention is directed.
The present invention provides a mechanically stabilized wall system having secure retaining means for maintaining reinforcement members in their proper positions within the retaining wall. Retaining walls constructed in accordance with the invention comprise a plurality of wall blocks that are stacked on top of each other in a plurality of ascending courses. Generally, each of the wall blocks is substantially identical in size and shape to simplify block fabrication and wall construction. Therefore, each of the blocks comprises an exterior face, an interior face, a top surface, a bottom surface, and opposed sides. The exterior faces of the blocks form the exterior surface of the retaining wall and typically are provided with an ornamental facing. In addition, the exterior face of each block normally slopes inwardly from the bottom surface to the top surface of each block.
The top and bottom surfaces of the blocks are typically parallel to each other such that the blocks can be stacked atop each other to form an upright wall. Similarly, the opposed sides of the blocks are normally parallel to each other such that a straight wall will be formed. The top and bottom surfaces of each block are provided with a lock channel and lock flange, respectively. The lock channel is defined by a front wall, a rear wall, and a channel bottom surface and the channel typically extends transversely across the top surface of each wall block. The front wall of this channel forms a frontal lip that extends obliquely toward the exterior face of the wall block. The frontal lip is normally curved such that a first substantially arcuate edge of the channel is formed. Positioned opposite the front wall, the rear wall of the lock channel extends obliquely toward the interior face of the wall block. Like the front wall, an upper extent of the rear wall is typically curved so as to form a second substantially arcuate edge of the lock channel. Provided in the channel bottom surface is a longitudinal notch that usually extends the full length of the lock channel.
The lock flange is defined by a front surface, a rear surface, and a bottom surface and typically extends transversely across the bottom surface of the wall block. Each of the front and rear surfaces extend obliquely toward the exterior face of the wall block such that the lock flange itself extends obliquely towards the exterior face. The front surface of the flange is specifically sized and shaped for mating engagement with the front wall and frontal lip of the lock channel.
Positioned between at least one pair of mating courses of wall blocks is a reinforcement member. This reinforcement member is of known construction and typically extends from the exterior surface of the retaining wall, into the lock channel, and past the interior surface of the retaining wall to extend into the soil. Placed on top of the reinforcement member in the lock channel is a retaining bar which secures the reinforcement member in place between the courses of the wall. The retaining bar is sized and shaped for easy insertion into the lock channel. In a preferred arrangement, the retaining bar has a top surface, a bottom surface, a first upright surface, a second upright surface, a first oblique surface, and a second oblique surface. Normally, the top and bottom surfaces are parallel to each other as are the first and second oblique surfaces. Configured in this manner, the retaining bar fits closely between the front and rear walls of the channel so that the first upright surface and the second oblique surface of the retaining bar hold the reinforcement member against the front and rear walls of the channel, respectively. So disposed, the retaining bar prevents the reinforcement member from being removed from the retaining wall.
In constructing a retaining wall according to the present invention, a plurality of starting blocks are usually aligned along the length of a leveling pad formed on the construction site. Each of the starting blocks is provided with a lock channel in its top surface just as the above described wall blocks. However, since the starting blocks form the first course of the wall, they need not be provided with lock flanges.
After the starting course has been formed, the first course of wall blocks is constructed. Each of the wall blocks is placed on top of one or more starting blocks with the lock flanges of each wall block extending into the lock channels of the lower blocks. The upper blocks are then slid forward along the starter blocks until the lock flanges of the upper blocks engage the front walls of the lock channels provided in the starter blocks. Specifically, the front surface of the lock flanges and frontal lip of the lock channels mate such that the lock flanges extend underneath the frontal lips. This mating relationship holds the wall blocks in place atop the starter blocks and prevents them from tipping forward, thereby providing an integral locking means for the blocks. After the first course of wall blocks has been formed, the backfill soil can be poured into place behind the blocks. In that the blocks are locked into place with the mating relationship of the frontal lips and lock flanges, the pouring of the soil can be accomplished without having to provide additional stabilization to the blocks to prevent them from toppling forward.
Once the proper amount of soil has been poured, additional courses are laid in the manner described above. Typically, a reinforcement member is laid between every other course of blocks, although it will be appreciated that greater or fewer reinforcement members can be provided depending upon the particular reinforcement needs of the construction site. As noted above, the reinforcement member is positioned so that it extends from the exterior surface of the wall and into the lock channel before extending into the backfill soil. To lock the reinforcement member between the courses, a retaining bar is placed on top of the reinforcement member in the lock channel. When the next course of blocks is laid, the lock flange of the upper blocks extend into the lock channels so that they are positioned adjacent the retaining bar. When a tensile force is applied to the reinforcement member from the soil side of the retaining wall, the retaining bar is urged towards the interior surface of the retaining wall, causing the second oblique surface to press the reinforcement member against the rear wall of the channel, locking it in place.